Motor vehicle fuel tanks provide not only a reservoir for fuel but also must have accommodation for adding fuel, delivering fuel (i.e., to the engine) and monitoring the amount of the fuel therein. It has become a common practice to combine the fuel delivery and monitoring functions via a fuel pump module which is removably interfaced with an opening of the fuel tank outershell.
FIG. 1 depicts an example of a motor vehicle fuel tank 10 having, by way of example, a saddle shape featuring two fuel sumps 10a, 10b. The fuel tank outershell 12 is provided with first and second openings 12a, 12b, each opening being disposed over a respective fuel sump 10a, 10b. At the first sump 10a, and interfaced sealingly with the first opening 12a, is a fuel pump module 14, and at the second sump 10b and interfaced sealingly with the second opening 12b is a secondary fuel transfer source 16 which is fluidically connected to the fuel pump module 14 via a transfer line 18.
The fuel pump module 14 is part of a by-pass fuel system. With respect to by-pass fuel systems, there are feed and by-pass fuel lines which loop the fuel back to the fuel pump module or loop the fuel within the fuel pump module. The term “by-pass fuel system” refers to both “return fuel systems” and “mechanical returnless fuel systems”. In the case of returnless fuel systems, a fuel pressure regulator is included with the by-pass fuel loop, being located within the fuel pump module.
FIG. 2 depicts a schematic representation of the functional aspects of a fuel pump module 20 utilized in the prior art, as for example in the manner of fuel pump module 14 in FIG. 1 with respect to a fuel tank of a return fuel system. A module reservoir 22 is defined by a plastic module sidewall 20a. A fuel pump 24 draws reservoir fuel FR through a strainer 26 in the module reservoir, and the strained fuel FS is then pumped by the fuel pump 24, and the strained pumped fuel FP is then delivered to the engine 40 via an inline fuel filter 28 and feed fuel line 30.
The by-pass fuel system continuously pumps fuel, and any amount not utilized by the engine is returned as a by-pass strained fuel FB to the fuel pump module 20 by an intersecting by-pass fuel line 32 with a fuel pressure regulator 34 located between the fuel pump 24 and the engine 40. The by-pass strained fuel FB is dumped via a standpipe 36 into the module reservoir 22. In this regard, because the by-pass strained fuel FB dumpingly mixes with the reservoir fuel FR already in the module reservoir, it becomes no longer separate as a uniquely identifiable entity and becomes merely a mixed aspect of the reservoir fuel FR component, wherein all of the reservoir fuel must be strained before entry to the fuel pump.
In that a conventional fuel pump module of a by-pass fuel system dumps and mixes the by-pass strained fuel FB with the reservoir fuel FR, all fuel entering into the fuel pump must be strained in order to remove any contaminants from the fuel regardless of the fact that some of the fuel may have been previously strained. This requirement to strain all fuel entering the fuel pump irrespective of past strain history of the fuel requires the fuel pump to work harder than it might otherwise have to if somehow the strained fuel could remain separate. Further, the mixing of the by-pass strained fuel FB with the reservoir fuel FR causes the strainer to pass therethrough more fuel, with attendant clogging aspects, than would otherwise be necessary if somehow the strained fuel could remain separated from the reservoir fuel and somehow be able to pass to the fuel pump without being re-strained.
Accordingly, it would be desirable for by-pass fuel systems if somehow the by-pass strained fuel could remain separate from the reservoir fuel after by-pass such that it would not have to be re-strained before entry to the fuel pump.